The mechanisms of cell surface recognition and adhesion, and the secondary events triggered by such interactions, will be investigated in Chlamydomonas reinhardi. In the mating reaction of this biflagellate alga, flagellar adhesion between gametes of opposite mating types triggers release of a cell wall lysin and activation of mating structures--two events necessary to prepare the gametes for fusion to form a zygote. 1) In combination with several proposed solubilization procedures, two quantitative adhesion assays will be used to detect and purify adhesive molecules. Adhesive and non-adhesive flagellar membranes will be compared by sodium dodecyl sulfate acrylamide gel electrophoresis in combination with isoelectric focusing. These techniques will also be used to determine if flagella which have been inactivated by adhesion and deadhesion have been covalently modified. In addition, cleavable bifunctional cross-linking reagents will be used to attempt to identify and isolate interacting adhesive molecules. 2) The mechanism of triggering of cell wall lysin release will be investigated, the lysin enzyme(s) will be isolated and characterized, and the composition of cell walls and their digestion products will be studied. 3) R.A. Bloodgood (J. Cell Biol., December, 1977) has described the bidirectional saltatory movement of marker particles in association with the surface of Chlamydomonas flagella. The potential role of this previously undescribed flagellar surface motility in the mating reaction will be investigated by use of microcinematographic recording techniques.